1. Field of the Invention
This invention relates to a device for assisting and/or taking over the pumping function of the heart, comprising a multilayer sheathing part configured for compressing the heart at least in certain sections, wherein the sheathing part has at least one stabilization layer for shaping the sheathing part, and at least one inner extensible augmentation layer, and wherein between the stabilization layer and the augmentation layer at least one cavity is formed, which is inflatable and deflatable by means of a fluid, for cyclic compression of the heart.
2. Description of Related Art
A device for pericardially assisting and/or taking over the cardiac activity of the above-mentioned type is known, for instance, from the German Patent Application DE 199 51 220 A1. This is a not very invasive, i.e., percutaneously implantable system, for mechanically assisting and temporarily replacing the pumping function of the heart. After probing of the pericardium, the device is inserted percutaneously into the pericardium, or at the end of an operation is surgically positioned inside the pericardium, and placed therein with a double membrane around the right and left ventricle. In a deflated state of the double membrane, the device is so thin that compression of neighboring organs is avoided. After implantation, the cavity of the double membrane is rhythmically loaded via a connecting tube with a fluid, which may be a gas (helium or CO2) or some appropriate liquid. Due to this rhythmical inflating and deflating of the cavity of the double membrane, and because the outer membrane, in contrast to the inner membrane, is not extensible, pressure transmission and compression of the heart via the double membrane enclosing the heart occurs. In doing so, blood from the right ventricle is expelled into the pulmonary artery, and simultaneously, from the left ventricle into the aorta, or if a pumping function of the heart is present, the systolic ejection work of the cardiac muscle is assisted.
A similar device—albeit operating epicardially—is known from the International Patent Application Publication WO 2005/110513 A1. This device also provides a double membrane for epicardially assisting and/or taking over cardiac activity, having an elastic inner membrane and a non-elastic outer membrane, as well as a closed cavity formed therebetween, which is inflatable and deflatable by means of a fluid, with a first chamber assigned to the right ventricle and a second chamber assigned to the left ventricle. The first chamber and the second chamber are connected together via at least one valve inside a dividing wall separating both chambers. As required, double membranes can be manufactured, which allow for the sole augmentation of the right ventricle, or—in another embodiment—of the left ventricle only, both while maintaining the possibility of assisting both ventricles simultaneously.
The devices described above are fastened directly to the heart and to the organs surrounding the heart inside the thorax, so that the devices are constantly in direct contact with the heart surface. However, mounting and fixing the devices to the delicate tissue of the heart, lungs, and great vessels is only possible in a limited way because of the organs' macro and micro-anatomical nature. Frictional forces occurring between the device and tissue can at very short term, within hours and days, lead to considerable irreparable tissue damage; penetrations of the ventricles and great vessels inside the thorax will result in the patient's death within minutes. Also, when mounting and fixing the devices directly to the heart, the intrinsic heart action may be hindered or affected, with the heart, due to the mechanical pumping function thereof, exhibiting cyclic shortening or lengthening of the heart axis with simultaneous spiral-like rotation about the heart axis. Another challenge for devices to be introduced inside the thorax is due to the spatial and positional relations between organs (heart, lung, great vessels) on the one hand, as well as between thoracic organs and the inner wall of the thorax on the other hand. They offer very limited possibilities for deploying instruments or devices introduced into the thorax at or around the heart or for bypassing the heart.